Multi-Part Buffer Tubes, Methods of Manufacturing the Same, and Firearms Including the Same

ABSTRACT

Multi-part buffer tubes, methods of manufacturing the same, and firearms including the same are disclosed. In embodiments the multi-part buffer tube includes a cap, and a body that includes a tube. The tube may include a wall with an outward facing side, an inward facing side, a first end, and a second end. The inward facing side of the wall may define a cavity for receiving a buffer and a buffer spring for a firearm. The cap that is coupled to the body in any suitable manner For example, at least a portion of the cap may be disposed within a channel formed in the inward facing side of the tube, e.g., proximate the first end of the wall.

FIELD

The present disclosure relates to buffer tubes for firearms, methods of forming the same, and firearms including the same. More particularly, the present disclosure relates to multi-part buffer tubes, methods of forming the same, and firearms including the same.

BACKGROUND

Modular gas operated small arms such as the M16, the M4, and the AR-15, are popular with civilians, law enforcement agencies, militaries, and the like. Part of their appeal is attributable to their modular nature, which allows users to customize the weapon to achieve a desired aesthetic and/or functional goal.

FIGS. 1A, 1B, and 2 illustrate one example of a modular short barrel AR-15 style rifle consistent with the prior art. As best shown in FIG. 1A, rifle 100 includes a lower receiver 101, an upper receiver 103 coupled to the lower receiver 101, a buttstock 105, and a buffer assembly. As shown in FIGS. 1B and 2 , the buffer assembly includes a buffer tube 111 (also known as a receiver extension), a buffer spring 115, and a buffer 117. The buffer tube 111 is configured to be installed in a buffer tube receiving aperture of lower receiver 101—typically with an end plate 107 and a castle nut 109. As best shown in FIG. 2 (which depicts a prior art buffer assembly), buffer tube 111 includes a cylindrical portion with a first end 102 and a second end 104. The first end 102 includes a port that is configured to allow gas to escape when buffer 117 is moved towards the first end 102 when rifle 100 is fired. Second end 104 includes an opening that is configured to receive buffer spring 115 and buffer 117 therein. Buffer tube 111 further includes a keyed protrusion 113 that extends from the cylindrical portion of the buffer tube 111 at a six o'clock position. The keyed protrusion 113 includes a plurality of spaced recesses that are configured to interact with a retractable bolt to lock buttstock 105 in a desired position with respect to the buffer tube 111. The cylindrical portion of buffer tube 111 may include a threaded portion 119, which can be used to couple buffer tube 111 to lower receiver 101, e.g., via interaction with corresponding threads in the buffer tube receiving aperture.

During normal operation of an AR-15 style rifle such as rifle 100, propellant in cartridge ammunition is detonated to produce gas that forces a bullet out of the barrel of the rifle. Before the bullet exits the barrel a portion of the gas enters a gas port in the barrel.

The gas port directs the gas into a tube, which conveys the gas into a cylinder between the bolt carrier and the bolt of the rifle. The gas drives the bolt carrier rearward (towards the buttstock 105). This forces the buffer 117 (which is pressing against the bolt carrier) rearward against buffer spring 115 and toward first end 102, allowing the bolt carrier to continue to move rearward. During this continued rearward movement of the bolt carrier, a spent cartridge is extracted from the chamber and expelled through an ejection port of the rifle. When the bolt carrier reaches a rearmost position (e.g., when the buffer 117 contacts first end 102), the compressed buffer spring 115 expands, driving the buffer 117 forward with enough force to drive the carrier bolt forward toward the chamber. During the return of the bolt carrier towards the chamber, a new cartridge is picked up by the bolt from a magazine and pushed forward to chamber the new cartridge.

Buffer tubes such as buffer tube 111 are single-piece (i.e., monolithic) parts, meaning that all parts of the buffer tube are integrally formed from a single piece of metal. For example, manufacturing of buffer tube 111 may begin with a metal billet, such as a billet of aluminum or titanium. The billet may be machined (e.g., using lathes, drills, milling machines, honing machines, grinders, etc.) to form a single piece part that includes the cylindrical portion, keyed protrusion 113, and first end 102 of buffer tube 111. Although traditional single-piece buffer tubes are useful, machining such buffer tubes from a metal billet may require the use of specialized machinery and personnel, which can lead to increased manufacturing costs. Since billets are typically solid, the manufacturing process results in the generation of considerable metal waste, which must be disposed of or recycled.

Accordingly, a need remains in the art for improved buffer tubes for use in gas operated firearms, and methods of making the same. The present disclosure is aimed at such needs.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features of this disclosure, and the manner of attaining them, will become more apparent and better understood by reference to the following description of embodiments described herein taken in conjunction with the accompanying drawings, wherein:

FIG. 1A is a schematic view of a prior art AR-15 style rifle;

FIG. 1B is a cross sectional diagram of part of a prior art lower receiver and buffer assembly of an AR-15 style rifle;

FIG. 2 is a cross sectional diagram of a prior art buffer assembly;

FIG. 3A is a perspective view of one example of a multi-part buffer tube consistent with the present disclosure, including a tube and a cap;

FIG. 3B is another perspective view of the multi-part buffer tube of FIG. 3A;

FIG. 3C is a side view of the multi-part buffer tube of FIG. 3A;

FIG. 3D is a bottom view of the multi-part buffer tube of FIG. 3A;

FIG. 3E is a first exploded perspective view of the multi-part buffer tube of FIG. 3A;

FIG. 3F is a second exploded perspective view of the multi-part buffer tube of FIG. 3A;

FIG. 3G is a detail view of area X in FIG. 3F;

FIG. 3H is a cross sectional view of the multi-part buffer tube of FIG. 3A, taken along plane A-A in FIG. 3E with the cap removed;

FIG. 3I is a perspective view of one example of a cap for use with a multi-part buffer tube consistent with the present disclosure;

FIG. 3J is another perspective view of the cap of FIG. 3I;

FIG. 3K is a detail view of area Y in FIG. 3H, with a cap installed;

FIG. 4 is a flow diagram of example operations of one example of a method of manufacturing a multi-part buffer tube consistent with the present disclosure;

FIG. 5A is a cross sectional diagram of one example of a method of joining a tube and cap to form a multi-part buffer tube consistent with the present disclosure;

FIG. 5B is a cross sectional diagram showing an example of a result of joining a tube and cap to form a multi-part buffer tube in the manner shown in FIG. 5B; FIG. 6 is an image of part of a buffer tube consistent with the present disclosure, showing an interface between a tube and cap.

FIG. 6 is a photograph of a cross section of an end of a multi-part buffer tube consistent with the present disclosure.

FIG. 7 depicts an example of an alternative configuration of a tube portion of a multi-part buffer tube consistent with the present disclosure.

FIG. 8 is a cross-sectional diagram of another example of a multi-part buffer tube consistent with the present disclosure.

DETAILED DESCRIPTION

The present disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention(s) herein may be capable of other embodiments and of being practiced or being carried out in various ways. Also, it may be appreciated that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting as such may be understood by one of skill in the art.

As described in the background, traditional buffer tubes are single-piece (i.e., monolithic) parts that are generally manufactured by machining a block of material such as a metal billet. Although single-piece buffer tubes are useful, how they are made can increase their cost and generate substantial waste. With that in mind, aspects of the present disclosure relate to multi-part buffer tubes, firearms including the same, and methods of forming the same. As will become apparent from the following disclosure, the multi-part buffer tubes described herein may be manufactured in accost effective manner that generates less waste than the manufacturing process of traditional buffer tubes, while still achieving desired performance.

In embodiments the multi-part buffer tubes described herein include a body that includes a tube. The tube may include a wall with an outward facing side, an inward facing side, a first end, and a second end. The inward facing side of the wall may define a cavity for receiving a buffer and a buffer spring for a firearm. The buffer tubes described herein further include a cap that is coupled to the body in any suitable manner. For example, at least a portion of the cap may be disposed within a channel formed in the inward facing side of the tube, e.g., proximate the first end of the wall.

In embodiments the multi-part buffer tube further includes a lip between the channel and the first end of the tube. The lip may have an inner diameter ID1, the channel may have an inner diameter ID2, wherein ID2 is greater than ID1. In those or other embodiments the cap includes a first cap part and a second cap part wherein at least a portion of the second cap part may be disposed within the channel. The first cap part may have an outer diameter OD3, the second cap part may have an outer diameter OD4, wherein OD4 is greater than OD3. In embodiments, the first cap part is positioned proximate the lip and OD3 is the same or about the same as ID1. In those or other embodiments, the cap may further include a cap groove between the first cap part and the second cap part.

The cap may include a first cap side facing away from the cavity of the tube, and a second cap side that faces towards the cavity. In such embodiments the first side may be coplanar or substantially coplanar with a surface of the first end of the tube.

The multi-part buffer tubes described herein may also include threads that are formed on the outward facing side of the tube. In such instances the first end of the tube may have an outer diameter OD1 and the threads may have an outer diameter OD2, wherein OD2>OD1.

Another aspect of the present disclosure relates to methods of forming multi-part buffer tubes for a firearm. In embodiments, the methods include providing a body that includes a tube that includes a wall with an outward facing side, an inward facing side, a first end, a second end, and a channel formed in the inward facing side proximate the first end, wherein the inward facing side defines a cavity for receiving a buffer and a buffer spring for a firearm. The method further includes providing a cap, and coupling the cap to the tube within the cavity. In embodiments, coupling the cap to the tube includes deforming (e.g., by compressing) the cap such that at least a portion of the cap is disposed within the channel. The cap and tube may have any or all the features of the caps and tubes described herein in connection with a multi-part buffer tube.

Another aspect of the present disclosure relates to a firearm. The firearm includes a lower receiver, an upper receiver, and a multi-part buffer tube. The multi-part buffer tube may include any or all the features of the multi-part buffer tubes described herein.

Reference is now made to FIGS. 3A-3K, which provide various views of one example of a multi-part buffer tube consistent with the present disclosure. With reference to FIGS. 3A and 3B, multi-part buffer tube 300 includes body 310 that includes tube 301 and a keyed protrusion 313. The tube 301 includes a wall (not separately labeled) having a first end 302 and a second end 304. As best shown in FIGS. 3A and 3H, the wall of tube 301 has an outward facing side 350 and an inward facing side 360, wherein the inward facing side 360 defines a cavity (e.g., a cylindrical cavity) for receiving a buffer and a buffer spring of a firearm therein. Tube 301 further includes a first opening 306 that is at least partially defined by the first end 302, and a second opening 307 that is at least partially defined by the second end 304.

The keyed protrusion 313 extends from tube 301 (e.g., at a six o'clock or other position). In general, keyed protrusion 313 is configured to facilitate coupling of multi-part buffer tube 300 to a firearm, such as a firearm receiver, buttstock, or combination thereof. For example, the keyed protrusion 313 may include a groove and/or a plurality of recesses (not labeled) that are configured to set the position of a buttstock or receiver of a firearm relative to the multi-part buffer tube 300.

As further shown in FIGS. 3A, 3B, and 3C, tube 301 may further include threads 319 or another mechanical fastener formed or coupled to the outward facing side 350, and which is/are located proximate to the second end 304. In such instances and as best shown in FIG. 3C, the first end 302 of tube 301 may have an outside diameter OD1 and the threads 319 may have an outside diameter OD2, wherein OD2 is greater than OD1. Without limitation, OD2 is preferably greater than OD1. In any case, at least a portion of the cavity within tube 301 may have an inside diameter ID1, wherein ID1 is sized such that the cavity can receive a buffer and a buffer spring of a firearm therein. ID1 may also be sized such that the first end 302 may receive at least a portion of a cap, as discussed below.

Multi-part buffer tube 300 further includes a cap 305 that is coupled to tube 301. Cap 305 is generally configured to provide a surface against which a buffer spring may be compressed when a bullet is fired by a firearm in which multi-part buffer tube 300 is installed. Cap 305 may be coupled to tube 301 in any suitable manner, such as via an interference fit with tube 301, a weld, an adhesive, a mechanical fastener, combinations thereof, and the like. For example, cap 305 may be coupled to tube 301 via threads, wherein the threads on Cap 305 may have a larger or smaller diameter than mating threads on ID1 of tube 301. Without limitation, cap 305 is coupled to tube 301 at least in part due to interference between a part of cap 305 and a part of tube 301. Notably and as distinguished from traditional buffer tubes, tube 301 and cap 305 are not integral parts, but rather are at least two distinct pieces that are joined together to form a multi-part buffer tube consistent with the present disclosure. This may be evidenced by the presence of a seam or other interface between the cap 305 and the tube 301.

Without limitation, cap 305 is configured to be installed proximate first end 302 of tube 301, as best shown in FIG. 3A. Preferably, cap 305 is sized and configured such that a first cap side 321 thereof is parallel or substantially parallel to a surface of first end 302 of tube 301 when cap 305 is installed. In embodiments, cap 305 is sized and configured such that first cap side 321 is coplanar with the surface of first end 302, as best shown in FIG. 3K. Such a configuration is not required, however, and cap 305 may be configured differently.

As noted above, cap 305 is preferably coupled to tube 301 via an interference fit with tube 301. In that regard reference is made to FIG. 3G, which is a detail view of the first end 302 of tube 301, generally labeled as an area X in FIG. 3F. As shown, the first end 302 at least partially defines a first opening 306 of tube 301. The first opening 306 (like other portions of tube 301) may have an inside diameter ID1, which may be dimensioned in any suitable manner and is preferably configured such that at least a portion of cap 305 is receivable therein. In embodiments, ID1 is set such that at least a portion of cap 305 is parallel, substantially parallel, and/or coplanar with a surface of the first end 302 of tube 301. That concept is again best shown in FIG. 3K, which shows cap 305 as including first cap side 321 that is coplanar with a surface of first end 302.

As further shown in FIG. 3G, a channel 309 is formed in the inward facing side 360 of tube 301. Channel 309 is preferably positioned at a distance from the first end 302, such that a lip 308 is present between the channel and the first end 302. The position of channel 309 relative to the first end 302 may be set such that at least a portion of cap 305 (e.g., first cap side 321) is parallel, substantially parallel, and/or coplanar with a surface of the first end 302 of tube 301 when cap 305 is installed therein. In embodiments and as shown channel 309 continuously extends circumferentially around the inward facing side 360 of the cavity within tube 301. In such instances and as best shown in FIG. 3H, the channel 309 may have an inside diameter ID2 that is greater than the inside diameter ID1, which in this case is the inside diameter of lip 308 (and optionally portions of the cavity other than the channel 309). Alternatively or additionally, channel 309 may include one or a plurality of channels that each extend only partially around the circumference of inward facing side 360. This concept is shown in FIG. 7 , which depicts an alternative configuration of tube 301, in which channel 309 is replaced is replaced with a plurality of channels 709 that extend partially around the circumference of inward facing side 360. In any case, channel 309 is configured to receive at least a portion of cap 305 therein, such that an interference fit joint is present between cap 305 and tube 301 or, more specifically, between cap 305 and at least a portion of channel 309.

The cross-sectional shape of channel 309 is not limited, and channel 309 may have any suitable cross sectional shape. For example, channel 309 may have a one, two, three, four, or more sided geometric cross sectional shape, an irregular cross sectional shape, or a combination thereof. Without limitation, in embodiments channel 309 has a c-shaped (three sided) cross sectional shape. The depths of channel 309 is also not limited, and channel 309 may have any suitable depth provided it is less than the thickness of the wall defining the cavity within tube 301. In embodiments, the depth of channel 309 ranges from greater than 0 to less than or equal to about .0.050 inches, such as from greater than 0 to about 0.040 inches, greater than 0 to about 0.030 inches, or even greater than 0 to about 0.015 inches.

For example, in embodiments cap 305 and tube 301 may be initially provided as separate parts, e.g., as shown in FIG. 3E and 3F. For example, and with references to FIGS. 3I and 3J, cap 305 may include a first cap side 321 and a second cap side 323. In general, and as best shown in FIG. 3K, first cap side 321 is configured to face away from the cavity in tube 301 when cap 305 is installed therein. In contrast, second cap side 323 is configured to face toward the cavity in tube 301 when cap 305 is installed therein. Cap 305 may further include a first cap part 325 (which includes first cap side 321), a second cap part 327 (which includes second cap side 323), and cap groove 329 therebetween. In embodiments, second cap side 323 (or more particularly, second cap part 327) includes at least one stepped cap structure 330. Stepped cap structure 330 may be in the form of a chamfer (as shown) or another suitable structure such as a bevel, a step, a protrusion, etc. When used, stepped cap structure 330 may be configured to facilitate coupling of cap 305 and tube 301, as described later. Other embodiments may have no stepped structure at all and simply have a generally flat or planar surface. Cap 305 further includes a through hole (shown but not labeled) that is configured to allow gas to escape when a buffer and buffer spring are compressed toward cap 305 within multi-part buffer tube 300, e.g., during operation of a firearm in which multi-part buffer tube 300 is installed.

With reference to FIGS. 3I, 3J, and 3K, first cap part 325 may have a first circumferential side 331, and second cap part 327 may have a second circumferential side 333. Prior to being joined with tube 301, the first and second circumferential sides may have an outside diameter OD3 that is the same or substantially the same as the inside diameter ID1 of the first end 302 of tube 301. In such instances, the cap groove 329 may have an outside diameter than is less than OD3. When configured in that manner, cap 305 may be inserted into the first opening 306 in first end 302, with second cap side 323 oriented towards the cavity within tube 301, and the first cap side oriented away from the cavity within tube 301. At least a portion of cap 305 may then be deformed into channel 309, resulting in the formation of an interference fit joint. For example, second cap part 327 may be deformed outwards, such that at least a portion of the material forming second cap part 327 is disrupted into channel 309. Put differently, second cap part 327 may be deformed such that its outside diameter increases from ≤OD3 and ≤ID1 to an outside diameter OD4, wherein OD4>ID1, OD4>OD3, and OD4 ≤ID2 (i.e., the inner diameter of channel 309). That concept is shown in FIG. 3K, which illustrates second cap part 327 as having an outside diameter OD4 that is greater than the outside diameter OD3 of first cap part 325 and the inner diameter ID1 of tube 301, wherein OD4 is less than or equal to the inside diameter ID2 of channel 309.

As noted above, cap 305 may include a cap groove 329 between a first cap part 325 and a second cap part 327. In general, cap groove 329 is configured to facilitate deformation of second cap part 327 into channel 309 during the formation of multi-part buffer tube 300. For example, and as will be described further below in connection with FIGS. 4, 5A, and 5B, second cap part 327 may be deformed by compressing cap 305 between a compression pin and a compression support. Because cap groove 329 has an outer diameter that is less than the outer diameter OD3 of the first and/or second cap parts 325, 327, cap groove 329 creates a weak point in the structure of cap 305 creating a stepped portion where second cap part 327 is distinctly separated from first cap part 325. This stepped portion in some embodiments may improve engagement between channel 309 and second cap part 327. As a result, when cap 305 is compressed, cap 305 deforms in the region corresponding to cap part 327, allowing at least part of second cap part 327 to move radially outward and into channel 309. Additionally, cap grove 329 also may provide an improved engagement surface that provides better engagement with channel 309 when cap part 327 is deformed into cap groove 329. In embodiments and as shown in FIG. 3K, at least a portion of cap groove 329 may remain following deformation of cap 305. Cap groove 329 and the stepped cap structure are not required, however, and in embodiments are omitted from cap 305.

As noted above and as best shown in FIGS. 3I, 3J, and 3K, cap 305 may include at least one stepped cap structure 330, e.g., on second cap side 323. Like cap groove 329, stepped cap structure 330 may facilitate deformation of cap 305 (and, more particularly, second cap part 327) into channel 309 when cap 305 is subject to compression. The angle and depth of stepped cap structure 330 may be selected to achieve suitable infiltration of material of cap 305 into channel 309 upon deformation (e.g. by compression) of cap 305.

Cap 305 and tube 301 may be configured such that cap 305 is positioned in a desirable manner relative to one another when they coupled. For example, cap 305 and channel 309 may be configured such that following coupling of cap 305 to tube 301, first cap side 321 is parallel, substantially parallel, and/or coplanar with first end 302 of tube 301, as shown in FIG. 3K. As also shown in FIG. 3K, cap 305 may align or substantially align with the corresponding surfaces of tube 301, such that no or substantially no gaps are present between first circumferential side 331 and the corresponding surfaces of lip 308.

Moreover, and as also shown in FIG. 3K, in some embodiments when cap 305 is coupled to tube 301, the second circumferential side 333 of cap 305 align or substantially aligns with the corresponding inward facing surface of channel 309, such that no or substantially no gaps are present therebetween. In any case, an interface may be observed between cap 305 and tube 301 or, more specifically, between cap 305 and channel 309. This concept is shown in FIG. 6 , which is a photograph of a multi-part buffer tube 300 that has been cut in half along plane A-A shown in FIG. 3E, and which shows an interface 601 between cap 305 and channel 309.

Body 310, tube 301, and cap 305 may be formed from any suitable material. Non-limiting examples of such materials include metals such as aluminum, titanium, iron, and the like, and alloys such as steel, brass, and the like. Other materials may also be used, as would be understood by those of ordinary skill in the art. In embodiments, body 310, tube 301, and cap 305 are each formed from aluminum.

For the sake of illustration and ease of understanding, the description of FIGS. 3A-3K focused on an embodiment in which cap 305 is coupled to tube 301 via an interference fit between a portion of cap 305 and a channel 309 formed in an inward facing side of tube 301. While such a configuration is useful and has excellent performance, it is not required and the cap 305 and tube 301 may be coupled to one another in a different manner as noted above. For example, in embodiments channel 309 may be omitted from tube 301, cap 305 may include a cap channel (e.g., comparable to cap groove 329), and at least a portion of tube 301 may be deformed into the cap channel to form an interference fit that couples cap 305 to tube 301. This concept is shown in FIG. 8 , which is identical to FIG. 3K except that channel 309 is omitted from tube 301, cap 305 includes a cap channel 801, and a portion 803 of tube 301 is deformed into cap channel 801 to couple tube 301 and cap 305 to each other.

Another aspect of the present disclosure relates to a firearm that includes a multi-part buffer tube assembly consistent with the present disclosure. In embodiments the firearm includes at least a lower receiver, an upper receiver, and multi-part buffer tube consistent with the present disclosure. In embodiments, the firearm is a modular rifle such as an M4, M16, or AR-15 style rifle, but the present disclosure is not limited thereto. The construction of such rifles is well understood and thus is not described. In any case the multi-part buffer tubes used in such rifles have the same features as described above. As such, the features of such multi-part buffer tubes are not re-described in the interest of brevity.

Another aspect of the present disclosure relates to methods of making a multi-part buffer tube. In that regard reference is made to FIG. 4 , which is a flow diagram of example operations of one example method of making a multi-part buffer tube consistent with the present disclosure. As shown, method 400 begins at start block 401. The method may then proceed to optional block 403, pursuant to which a tube and cap with the tubes and caps described herein are provided as separate parts. For example, the operations of block 403 may include providing a cap having the features of cap 305 in FIGS. 3I and 3J and providing a tube with the features of tube 301 in FIGS. 3F, G, and H as separate parts. How the tube and cap are provided is not limited, and such parts may be provided in any suitable manner. For example, a cap may be provided by machining a cap with the features of cap 305 from a metal bar. Alternatively, a cap consistent with cap 305 may be formed by forging, casting, or another metallurgical process. In embodiments, a cap consistent with cap 305 in FIGS. 3I and 3J is provided by casting a cap that includes a first cap side 321, second cap side 323, first cap part 325, second cap part 327, cap groove 329, and stepped cap structure 330 as shown in FIGS. 3I and 3J, after which a through hole may be formed through first cap side 321, e.g., by machining. Similarly, a tube consistent with the present disclosure may also be provided in any suitable manner. For example, a tube may be provided by direct extrusion of a metal through a die, resulting in the formation of an extruded part that includes a body with a keyed protrusion and a tube that includes a cavity as described above. The extruded part may lack a channel 309, the details (e.g., recesses) of keyed protrusion 313, and/or threads 319 described above. Such features may be formed in the extruded part in any suitable manner, such as but not limited to machining, resulting in the formation of a tube with the features of tube 301 noted above. Alternatively, a tube may be formed by casting metal to form a cast part with a body, tube, and cavity as described above. The cast part may lack a channel 309, the details (e.g., recesses) of keyed protrusion 313, and/or threads 319 described above. Such features may be formed in the cast part in any suitable manner, such as but not limited to machining, resulting in the formation of a tube with the features of tube 301 noted above.

Following the operations of block 403 or if such operations are omitted (e.g., where a cap and/or tube are provided by a third party), the method may proceed to block 405, pursuant to which the cap and tube are joined. As noted above the cap and tube may be joined in any suitable manner. Without limitation, in embodiments the cap and tube are joined by deforming at least a portion of the cap to create an interference fit joint between the cap and the tube or, more particularly, between a channel formed in an inward facing side of the tube and the cap. For example, and as shown in FIG. 5A, a tube 301 and a cap 305 with the features described above may be provided. The cap 305 may be initially provided with a first cap part 325 and a second cap part 327, wherein the first cap part 325 and second cap part 327 have an outside diameter each have an outside diameter OD3 that is the less than or equal to the inside diameter ID1 of a lip 308 of the tube 301. A compression pin 503 may be extended into second opening 307 in second end 304 of tube 301. The cap 305 may inserted into first opening 306 in first end 302 and arranged on a first compression surface 504 of the compression pin 503. The first compression surface 504 may be configured to complement the shape of second cap side 323, and may include a stepped pin structure 506 (e.g., a chamfer, bevel, protrusion, etc.) as shown in FIG. 5A. At this time, the first compression surface 504 may be positioned within the cavity within tube 301 such that the entirety of cap 305 is within the cavity and the surface of first cap side 321 is below the level first end 302. Like stepped cap structure 330 and cap groove 329, stepped pin structure 506 is not required and in embodiments may be omitted. For example, in embodiments stepped pin structure 506 is omitted (regardless of whether stepped cap structure and cap groove 329 are present or are omitted). In such instances, compression surface 504 may be substantially flat, or have any other suitable shape that enables deformation of cap 305 into groove 309 as discussed below.

A compression support 505 may then be arranged over the first end 302. As generally shown in FIG. 5A, compression support 505 includes a second compression surface 508 that is configured to extend across and substantially parallel to first opening 306 in first end 302. In addition, second compression surface 508 is configured to provide a surface to press against the first cap side 321 during compression of cap 305. Compression support 505 further includes one or more sides 512 that extend at least partially along the outward facing side 350 of tube 301, as shown. In general, sides 512 are configured to support the outward facing side 350 of tube 301 proximate first end 302 during compression of cap 305, so as to limit or prevent deformation (e.g. buckling and/or bulging) thereof during compression of cap 305.

Once compression support 505 is positioned on the first end 302 as shown in FIG. 5A, compression pin 503 may be extended until first cap side 321 abuts second compression surface 508 of compression support 505. At this point cap 305 is pinned between the first and second compression surfaces 504, 508, and is positioned such that first cap side 321 is parallel, substantially parallel, and/or coplanar with the surface of first end 302, and the second cap part 327 is located proximate channel 309 such that a gap 511 is present between a side of channel 309 and second circumferential side 333 as shown in FIG. 5A. Compression pin 503 may then be further extended to compress cap 305 between first compression surface 504 and second compression surface 508, causing at least a portion of cap 305 to deform into channel 309 as previously described. The amount of compression force applied may vary, and may depend on the materials and configuration of cap 305 and tube 301. In embodiments, compression of cap 305 between first compression surface 504 and second compression surface 508 causes second cap part 327 to deform in a radially outward direction into channel 309, e.g., by moving second circumferential side 333 radially outwards. Following such deformation, second circumferential side 333 (or another part of cap 305) may have an outside diameter OD4 that is greater than the outside diameter OD3, as shown in FIG. 5B.

As noted above, first compression surface 504 may include a stepped pin structure (e.g., a chamfer, bevel, protrusion, etc.) 506. In embodiments, the angle and/or length of stepped pin structure 506 may differ from the angle and/or length of stepped cap structure 330, to facilitate radial outward deformation of second cap part 327 into channel 309. For example, the inside angle of stepped pin structure 506 may be greater than 0 to about 15 degrees steeper than the outside angle of stepped cap structure 330 at a point 530, to encourage such radially outward deformation of second cap part 327 into channel 309.

Returning to FIG. 4 , following the operations of block 405 the method may proceed to block 407 and end.

As used herein, the term “about” when used in connection with a number or a range, means +/−5% of the indicated number or the endpoints of the indicated range.

As used herein, the term “coplanar” when used to describe the positions of a first surface and a second surface, means that the first and second surfaces lie in and extend along the same plane. In contrast, the term “parallel” when used to describe the relative positions of a first surface and a second surface, means that the first surface lies along a first plane, and the second surface lies along a second plane that extends in the same direction as the first plane but which is offset from the first plane. The term “substantially parallel” means that the first and second surfaces extend along planes that are offset from one another and which are within +/−5 degrees of parallel relative to one another.

The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. Each and every page of this submission, and all contents thereon, however characterized, identified, or numbered, is considered a substantive part of this application for all purposes, irrespective of form or placement within the application. This specification is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of this disclosure. 

What is claimed is:
 1. A multi-part buffer tube for a firearm, comprising: a body comprising a tube, the tube comprising a wall with an outward facing side, an inward facing side, a first end, and a second end; and a cap coupled to the tube by way of deformation to form an interference fit joint; wherein: the inward facing side of the wall defines a cavity for receiving a buffer and a buffer spring; and at least a portion of the cap is disposed within a channel formed in the inward facing side proximate the first end of the wall.
 2. The multi-part buffer tube of claim 1, further comprising a lip between the channel and the first end; wherein: the lip has an inner diameter ID1; the channel has an inner diameter ID2; and ID2>ID1.
 3. The multi-part buffer tube of claim 2, wherein: the cap comprises a first cap part and a second cap part; and at least a portion of the second cap part is disposed within the channel.
 4. The multi-part buffer tube of claim 3, wherein: the first cap part has an outer diameter OD3; the second cap part has an outer diameter OD4; and OD4>OD3.
 5. The multi-part buffer tube of claim 4, wherein: the first cap part is positioned proximate the lip; and OD3 equals or is about equal to ID1.
 6. The multi-part buffer tube of claim 3, wherein the cap portion further comprises a cap groove between the first cap part and the second cap part.
 7. The multi-part buffer tube of claim 4, wherein the cap portion further comprises a cap groove between the first cap part and the second cap part.
 8. The multi-part buffer tube of claim 3, wherein: the cap portion comprises a first cap side facing away from the cavity and a second cap side facing towards the cavity; and the second cap side comprises at least one stepped cap structure.
 9. The multi-part buffer tube of claim 3, wherein: the cap portion comprises a first cap side facing away from the cavity and a second cap side facing towards the cavity; and the first cap is coplanar or substantially coplanar with the first end.
 10. The multi-part buffer tube of claim 1, further comprising threads formed on the outward facing side of the wall proximate the second end; wherein: the first end has an outer diameter OD1; the threads have an outer diameter OD2; and OD2>OD1.
 11. A method of manufacturing a multi-part buffer tube for a firearm, comprising: providing a body comprising a tube, the tube comprising a wall with an outward facing side, an inward facing side, a first end, a second end, and a channel formed in the inward facing side proximate the first end, the inward facing side defining a cavity for receiving a buffer and a buffer spring of a firearm; providing a cap; and coupling the cap to the tube within the cavity by way of deformation to form an interference fit joint.
 12. The method of claim 11, wherein coupling the cap to the tube comprises deforming the cap such that at least a part of the cap is disposed within the channel.
 13. The method of claim 11, wherein: providing the cap comprises providing a cap comprising a first cap part, and a second cap part, the first cap part having first outer diameter and the second cap part having a second outer diameter; and following said coupling, at least a portion of the second cap part has a third outer diameter that is greater than the second outer diameter.
 14. The method of claim 13, wherein the first outer diameter equals or is about equal to the second outer diameter.
 15. The method of claim 13, wherein: the tube further comprises a lip between the channel and the first end; the lip has a first inner diameter; and the channel has a second inner diameter than is greater than the first inner diameter.
 16. The method of claim 11, wherein coupling the cap to the tube comprises compressing the cap.
 17. A firearm, comprising a lower receiver, an upper receiver, and a multi-part buffer tube, the multi-part buffer tube comprising: a body comprising a tube, the tube comprising a wall with an outward facing side, an inward facing side, a first end, and a second end; and a cap coupled to the tube by way of deformation to form an interference fit joint; wherein: the inward facing side of the wall defines a cavity for receiving a buffer and a buffer spring; and at least a portion of the cap is disposed within a channel formed in the inward facing side proximate the first end of the wall.
 18. The firearm of claim 17, wherein the multi-part buffer tube further comprises a lip between the channel and the first end; wherein: the lip has an inner diameter ID1; the channel has an inner diameter ID2; and ID2>ID1.
 19. The firearm of claim 17, wherein: the cap comprises a first cap part and a second cap part; and at least a portion of the second cap part is disposed within the channel.
 20. The firearm of claim 19, wherein: the first cap part has an outer diameter OD3; the second cap part has an outer diameter OD4; and OD4>OD3.
 21. The firearm of claim 20, wherein: the first cap part is positioned proximate the lip; and OD3 equals or is about equal to ID1.
 22. The firearm of claim 19, wherein the cap portion further comprises a cap groove between the first cap part and the second cap part.
 23. The firearm of claim 19, wherein: the cap portion comprises a first cap side facing away from the cavity and a second cap side facing towards the cavity; and the second cap side comprises at least one stepped cap structure.
 24. The firearm of claim 19, wherein: the cap portion comprises a first cap side facing away from the cavity and a second cap side facing towards the cavity; and the first cap is coplanar or substantially coplanar with the first end.
 25. The firearm of claim 17, further comprising threads formed on the outward facing side of the wall proximate the second end; wherein: the first end has an outer diameter OD1; the threads have an outer diameter OD2; and OD2>OD1.
 26. The multi-part buffer tube of claim 1, wherein at least a portion of the cap is deformed into the channel to form the interference fit joint.
 27. The method of claim 11, wherein at least a portion of the cap is deformed into the channel to form the interference fit joint.
 28. The multi-part buffer tube of claim 17, wherein at least a portion of the cap is deformed into the channel to form the interference fit joint. 